Coupling system



Jan. '5, 1937. E, HARNETT y 2,066,771

COUPLINGV SYSTEM Filed July ll, 1935 -2 Sheets-Sheet 1 fa f/ 3a 37.3@ ff? i9 33 34 60 45 7 y INVENTOR.

n Jg 04m/EL HAR/V577 63 BY C I 4 ATTORNEY.

Jan. 5, 1937. D, E, HARNTT `2,066,777

COUPLING SYSTEM Filed July 11, .1935 z sheets-sheet-z AW/EL E, HARA/77 s ATTORNEY.

Patented Jan. `5, 1937 aci '6 1942 vvv-- PATENT OFFICE COUPLING SYSTEM Daniel E. Hai-nett, Tuckalioe,` N. Y., assigner t -Hazeltine Corporation, a corporation of Dela- Waffe Application July 11, 1935, Serial No. 30,777

13 Claims.

This invention relates to coupling systems and particularly to methods of and means for adjusting the self-inductance of inductively coupled windings of such systems without changing the coeiilcient of coupling therebetween.

While my invention is of general application, it is especially adapted for use in connection with tuned selector systems, such as the intermediate-frequency selector systems of superheterodyne radio receivers. g

By reason of necessary manufacturing tolerances and of differences in reflected and stray reactances, such as tube capacitances and wiring capacitances, it is necessary that circuits of a system which are to be tuned to the same frequency be aligned, that is, that their reactances be readjusted, after the system has been assembled. Heretofore, it has been the general practice to" accomplish such alignment by adjusting condensers of the circuits. While this practice has proved satisfactory to a certain extent, various objections are inherent thereto; It has been found, for instance, thatthe capacitances of adjustable condensers of the types ordinarily employed are subject to considerable variation with age, changes in temperature and humidity, and from shocks and vibration. Fixed condensers, on the other hand, are obtainable which are substantially more stable under similar conditions, and their use is therefore highly desirable. Such use, however, necessitates alignment of the circuits in which they are employed by the adjustment of -the inductances thereof. Ordinarily, the tuning inductances of such adjacent circuits serve also to couple the circuits in the system and any change of the inductances results in a corresponding change in the coupling between the circuits and the selectivity of the system. In general, however, it is essential that the coupling of the system be unaltered. The ideal arrangement, therefore, calls for a system including circuits employing fixed condensers and inductively coupled windings, the self-inductances of which may be varied withoutchanging the.

coupling therebetween.

An object of the present invention is to provide an improved method of and means for adjusting the self-inductance of inductively coupled windings of a coupling system without changing the coupling therebetween. A

More particularly, an obiect of the 'invention is to provide an improved methodof and means for adjusting the tuning Aof selector circuitsv embodying ilxed condensers and inductively coupled windings, by varying the self-inductances of the windings without changing the coupling therebetween;

Various other and further objects of, and advantages achieved by, this invention will be apparent from the description hereinafter set forth of certain approved embodiments thereof.

In accordance with the present invention, the self-inductances -of a pair of inductively coupled mndings are adjusted and the mutual inductance between the windings is simultaneously adjusted in the same sense and in such proportion as to .maintain the coupling therebetween substantially constant. In a preferred embodiment of the invention the windings are employed as tuning elements of tuned circuits of a selector system. Each of the windings is preferably divided into a plurality of sections and all of the sections are coaxially mounted on telescopically engag-` ing forms. For example, the proximate sections of the two windings may be relatively iixedly mounted on an intermediate form and the remote portions on relatively movable end forms. Telescopic movement of either end form relative to the intermediate form changes the relative position of the sections of the respective winding so as to vvary its self-inductance. With such an arrangement, the mutual inductance between the sectionsA of each winding is thus varied to change the self-inductance of the respective winding, that is, the inductance individual to a particularcircuit This variation is accompanied by al smaller change in the mutual inductance between the two circuits. The variation of the mutual inductance between the circuits may be of the order of the square root of the self-inductance variations, resulting in substantially constant coupling between the circuits.

In the accompanying drawings, Fig. l isa simplied circuit diagram illustrating the present invention; Fig. 2 is a side elevation of a coupling device embodying the invention; Fig. 3 is an end view of the device shown in Fig. 2; Fig. 4 is a longitudinal section of the device shown in Figs. 2 and 3, taken on the line 4-4 of Fig. 3, with the condensers omitted; Fig. 5 is a side elevation oi.'v

Fig. 6, with the condensers omitted; Fig. 8 is a'.

section oi' the device shown in Fig. 8, taken on the line I-III of Fig. 9, with the condensers omitted.

Referring in detail to Fig. 1, the invention is here diagrammatically illustrated as employed in connection with a selector system such as is commonly used in the intermediate-frequency amplier section of a superheterodyne radio receiver. This system comprises a coupling device I Il, which includes coaxially arranged primary and secondary windings II and I2, each divided into a Aplurality of sections, as indicated. The windings II and I2 are preferably mutually external,` that.

is, they are entirely separated physically and no part of either extends into or over the other. Fixed condensers I3 and I4 are connected across the windings II and I2, respectively, in' the usual manner, and input and output terminals I5 and I6 are connected across the primary and secondary circuits, respectively. A coupling is provided between the primary and secondary circuits, principally by mutual inductances between the proximate sections of the windings II and I2.

With the circuits just described syntonously tuned, a selector system is provided which, according to well-known'principles, is adapted to pass a band of frequencies symmetrical with respect to a.median frequency. To permit proper alignment of the circuits, means are provided whereby the self-inductance of each of the windings is adjustable by changing the mutual inductance between sections of each winding, which are relatively remote from the other winding, as indicated by the arrows in Fig. 1. The arrows are intended to denote that the mutual inductances between the outer end sections of the windings and their respective intermediate sections may be varied. The mutual inductance between the s'ections of the respective windings which are proximate to each other is, however, maintained unchanged. By varying the self-inductances of the windings in this manner, the total mutual inductance between the two circuits may be varied and suchrvariation may be of the order of the square root of the self -inductance variation of the windings, so that the coupling between the circuits remans substantially unchanged.

That the coupling will remain unchanged will be readily appreciated upon consideration of the well-known formula:

M k== 1/ LiL:l where k is the coeilcient of coupling; L1 and La. the self-inductances of the primary and secondary windings, respectively; and M, the mutual inductance between the windings.

For constant coupling:

=L= Mr lrqLl' #Lira v where L2 equals the self-inductance of the secondary winding after adjustment, and M' equals the mutual inductance after adjustment.A From this formula I derive:

` end forms I8 and 28. The form Il is rigidly secured to a supportingvend'plate 2|. The end form II includes an elongated stem 22, which telescopically extends into the form I l, and an enlarged head 23 of the same outer diameter as the form I8. An adjusting screw 24 is rotatably mounted in an opening 25 in the plate 2I and engages a threaded axial opening 26 formed in the stem 22. A suitable clip2l engages the screw at one side ofthe plate and, together with the head of the'screw at the other side of the plate, prevents aidal movement of the screw relative to the plate. It will be apparent that, by turning the screw 24, axial movement of the form I9 in either direction relative to the form I8 may be effected.

The form 28 is hollow and is telescopically mounted on the inner end portion of the form I8. A radially extending bracket 28 is secured to the form 20 and is provided with a threaded opening`29. An adjusting screw 3|! is held in the end plate 2I, similarly to screw 24, and engages the bracket 28 in its opening 29. The form 28 may be axially moved relative to the form I8 by rotation of itsl adjusting screw, in the same manner as the form I9.

as pies, which are connected in series. The pory tion 33 is mounted on the head 23 of the form I3, and the portions 34 and 35 are mounted on the form I8, as illustrated. In similar manner, the secondary winding I2 includes three separate sections 36, 3'I and 38 which are connected in series, the portion 36 being mounted on the form 20 and the portions 3l and 38 being mounted on the form I8. The intermediate sections 34, 35,31 and I 38 are thus relatively fixed, while the end sections 33 and 36 of the two windings are movable in either direction with their respective forms I3 and 20 upon rotation of their respective adjusting screws 24 and 38. The self-inductances of the windings II and I2 may thus be adjusted without changing the coupling between the windings, as above described.

As shown in Fig. 2, the coupling device I`I is preferably disposed within a tubular shield 39 and suitably secured to an end plate thereof by bolts 48. The condensers VI3 and I4, which' are connected across the windings, are also preferably disposed within the shield and rigidly secured on the coupling device I1 by suitable brackets.

In Figs. 5-7, there is illustrated a modified form of coupling device, indicated generally byv the numeral 4I. The device 4I includes a hollow cylindrical intermediate form 42, and two cylindrical end forms 43 and 44. 'Ihe form 43 includes a head of substantially the same diameter as the form 42, a central portion 43, which telescopically extends into the form 42, and an elongated stem 41 which extends through and beyond the form 42. 'I'he form 44 telescopically extends into the form 42 and is provided witha central bore through which extendsthe stern 41 ot the form 43. The form 44 includes an enlarged portion 43 of 'the same diameter as the form 42.

The form 42 is secured to aflange Il formed on an arm 3| of a substantially U-shaped bracket l2. The other arm 53 of the bracket i2 extends oppositethe adjacent ends of the form 44 and u.

` opening 62.

stem 41 and is provided with two threaded openings 54 and 55. An adjusting screw 56 is threaded in the opening 54 and extends into a recess axially formed in the stem 41 and is rotatably secured to the stem and held against axial movement relative thereto by means of a pin 51, which extends transversely through the stern 41 and engages an annular groove 58 formed in the end portion of the screw.

A guide block 59 is secured to the bracket 52 and is provided with a slot 6I) which extends in the same direction as the stem 41. An end of the pin 51 projects into the slot 60 and serves to prevent rotation of the form 43.

An enlarged end portion or ange 6I is formed onthe form 44 and is provided with a longitudinal A second adjusting screw 63 is threaded in the opening 55 and includes an end portion of relatively small diameter, which extends through the opening 62. A suitable clip 64 holds the form 44 against longitudinal movement relative to the screw 63.

Rotation of the screws 56 and 63 serves to effect movement of the forms 43 and 44, respectively,vrelative to the stationary form 42 in substantially the same manner as described with reference to the adjusting screws and forms of and supported similarly to the windings of the device I1, the outer winding portions 33 and 36v being carried bythe end forms 43 and 44, respectively, and the other winding'portions 34, 35, 31 and 38 being carried on the form 42, as shown.

In Figs. 8-10 there is illustrated a further modied form of coupling device, indicated generally bythe numeral 12. The device 12 is substantially the same as the device 4I shown in Figs. 5-7, excepting that the adjusting means for the end forms are differently constructed.

Those parts only of the device 12 which differ from the device 4I will be described in detail. A U-shaped yoke 13 is pivotally secured at the ends of its arms 14 to the bracket 52a, which corresponds to the bracket. 52 of the device 4I, by means of pins 15 which are passed through ears 16 formed on the ends of the arms 14 and through lugs 11 secured to the bracket 52a.

. Pin members 16 are secured to the inner sides ofthe arms 14 and pivotally engage the end of the form 44a at the opposite sides thereof. An internally threaded ring 13 is pivotally secured in an opening provided therefor in the cross member of the yoke 13, as illustrated/` An adjusting screw 30a is secured to the bracket 52 and is threaded in the ring 19 in substantially the same manner as the screw 30 is secured to the plate 2i and engages the bracket 26- in the device I1. The yoke arrangement described insures a symmetrical application of the actuating ,forces of the screw 30a upon the form 44a. so as to ob- /viate anytendency toward binding or eccentric movementrof this form during its adjustment.

An adjusting screw 24a is secured to the bracket 52a and engages the stem of the form 43a, respectively, substantially in the samev manner as the screw 24 is secured to the plate 2| and engages form I3 in the device I1. The adjusting screws 24a and 30a arer operable to effect relative movements of the forms of the ydevice 12 similarly to the adjusting screws of the other embodiments. -Likewise, the separate portions of the windings are similarly mounted on forms so that the respective outer end sections of the windings are moved inwardly and outwardly, relative to the intermediate sections thereof, by the rotation of the adjusting screws, while the intermediate portions areheld in xed relative positions..

A satisfactory embodiment of the present invention, constructed in the form of the devi'ce I1, shown in Figs. 2-4, may have the following speciilcations:

Windings II and I2- Y 6 coil portions--each portion 95 turns '1 strands No. 40 Litz S. S. C. universal wound gears 36/38; 5/4 i. d., 1A," w., impregnated.

Distance between portions 35 and 38 Distance between portions 34 and 35, 31

and 38 116" Range of motion of the portions 33 and 36 relative to portions 34 and 31 respectively Vs" Windings mounted in shielding can 1%" square 31/2" long.

Transformer to operate at approximately 460 kilocycles.

From the foregoing description it will be understood that the coupling devices herein disclosed are capable of being adjusted to vary the selfinductance of each of the sectionalized windings witnoutany appreciable change in the coupling therebetween. This is due to the small change in the Vmutual inductance betweenthe windings in the same sense and to a lesser degree than the change in the self-inductance of either or both of the adjusted windings. The small change vin mutual inductance is, in turn, due, in general, to the proportioning and spacing of the winding sections in the manner described in' the preceding paragraph, whereby the adjustable winding sections do not constitute the major portion of the total inductance of their respective windings. In certain applications a considerable percentage departure in the mutual induotance between the two windings from the preferred square-root relationship is tolerable. For example, in the application mentioned, wherein -the device is used as a means for aligning the intermediate-frequency amplifier stages of a superheterodyne receiver, a change in the mutual inductance which, together with the corresponding changes inthe self-inductances ofthe windings, results in a percentage change in the coupling of the order of a few per cent, such, for example, as a change from .02 to .0205, does not adversely affect the operation ofthe receiver. The relative importance of the above factors is, of course, determined by the particular system or applicationvin which the coupling device is to be used.

While certain preferred embodiments of the invention have been heretofore described, it will be understood that vmany and various changes and modications in the application of the invention, and in the form, structure and parts of the various embodiments thereof, may be made without departing from the spirit of the invention. For instance, the invention is not conned to changing the self-inductance of the respective circuits by varying the relative positions of portions of the coils. but the principles of the invention may be practiced in various other suitable ways, as, for example, by changing the self-inductances oi the individual windings by adjusting the relative positions of magnetic cores employed in connection with the remote sections of the windings. It will also be apparent that, if desired, only one of the windings may Y be made adjustable. Further, any suitable number of separate winding sections may be utilized with either one or a greater part o! the total number of sections of each winding held fixed and with either one or a greater part oi the total number of the portions movable. It will, therefore, be understood that the appended claims are intended to cover all and any such applications, changes and modincations as fall fairly within the true spirit of the invention.

What is claimed is:

l. A coupling system comprising a pair of inductively coupled windings and means for adjusting the self-inductance of one of said windings without substantially changing the coupling therebetween, comprising means for varying the self-inductance of said one of said windings independently of and without appreciably changing the self-inductance of the other oi' said windings and simultaneously varying the mutual inductance between said windings in the same sense and in such proportion as to maintain said coupling substantially constant.

2., A coupling system comprising a pair of inductively coupled windings and means for adjusting the self-inductance o1' one oi said windings without substantially changing the coupling therebetween, comprising means for varying the self-inductance of said one of said windings independently of and without appreciably changing the self-inductance of the other of said windings and simultaneously varying the mutual inductance between said windings as the order of the square root of said self-inductance variation.

3. A couplingl system comprising a pair of inductively coupled windings and means for adjusting the self-inductance oi one of said windingsy without substantially changing the coupling therebetween, comprising means for varying the mutual inductance between certain ot the turns of said one of said windings independently of and without appreciably changing the self-inductance of the other of said windings and simultaneously varying the mutual inductance between said coupled windings in the same sense and in such proportion as to maintain said coupling substantially constant.

4. A coupling system comprising a pair of inductively coupled windings having relatively proximate portions and relatively remote portions, and means for adjusting the self-inductance of one of said windings without substantially changing the coupling therebetween, comprising means for adjusting the relative positions of portions of said one oi' said windings while main-'- taining the respective proximated portions o! said coupled windings relatively fixed.

5. A couplingl system comprising a pair oi inductively coupled mutually external coaxial windings, each oi said windings having a plurality of substantially similar serially connected sections, y and means for adjusting the self-inductance of either of said windings without substantiallyv changing the coupling thu'ebetween, comprising means for adjusting the relative positions o! saidsections so as to vary the muhnl inductance therebetween while maintaining'oonstant the mutual inductance between the respective proximate portions o! said two windings.

6.A eouplingsystemcomprisingapairofinductively coupled, mutually external, coaxial windings and means for adjusting the self-inductance of one oi' said windings without substantially changing the coupling therebetween, comprising means for varying the mutual inductance between portions of said one of said windings relatively remote from the other oi said windings while maintaining substantially constant the mutual inductance between the respective proximate portions of said coupled windings.

7. A coupling device comprising a plurality of forms, a pair of inductively coupled windings carried on said forms, said windings having proximate portions carried by one oi said forms and one of said windings having another portion thereof carried by` a second of said forms, and means for adjusting the relative positions of said two forms to vary the self-inductance of said one winding independently o! and without appreciably changing the self-inductance of the other winding and simultaneously to vary the mutual inductance between said windings in the same sense and in such proportion as to maintain said coupling substantially constant.

8. A coupling device comprising a plurality oi telescopically engaging forms, a pair of inductively coupled windings carried by said forms, said windings having proximate portions carried by one oi said forms and one of said windings having another portion thereof carried by a second of said forms, and means for telescopically moving one of said two forms relative to the other to vary the self-inductance of said one winding and simultaneously to vary the mutual inductance between said windings in the same sense and in such proportion as to maintain said coupling substantially constant.

9. A' coupling device comprising three telescopically engaging forms, a pair of inductively coupled windings having proximate portions carried by an intermediate one of said forms and each of said windings having a second portion carried by another of said forms, and means for telescopically moving. either of said other forms relative to said intermediate form to vary the self-inductance of either oi said windings and simultaneously to vary the mutual inductance between said windings in the same sense and in such proportion as to maintain said coupling substantially constant.

10.l A selector system comprising two tuned circuits having xed capacitances and inductively coupled windings, and means for adjusting the tuning of one of said circuits without substantially changing the coupling therebetween, comprising means for varying the self-inductance oi the winding of said one of said circuits independently of and without appreciably changing the self-inductance of the other winding and simultaneously varying the mutual inductance between said windings `in the same sense and in such proportion as to maintain said coupling substantially constant.

11. The method of adjusting the self-inductance of one of a plurality of inductively coupled windings without substantially changing the coupling therebetween, which comprises varying the self-inductance of said one of said windings inldependently of and-without sppreciably changing the self-inductance of the other o! said windings and simultaneously varying the mutual inducti5 ance Abetween said windings as the order of the square root of said self-inductance variation.

f 12. In a coupling system comprising a plurality of coupled windings, the method of adjusting the self-inductance of one of said windings without substantially changing the coupling therebetween, which comprises varying the mutual inductance between certain of the portions of said one of said windings independently of and without appreciably changing the self-inductance of the other of said windings and simultaneously 'varying the mutual inductance between the respective windings in the same sense and in such 15 tially constant.

13. In a selector system comprising two tuned circuits having ilxed capacitances and inductively coupled windings, the method of adjusting the tuning of one of said circuits without substantially altering the coupling therebetween, which comprises varying the self-inductance of the windingl of said one of said circuits independently of and without appreciably changing the selfinductance of the winding of the other of said circuits and simultaneously varying the mutual inductance between the respective windings in such proportion as to maintain said coupling substantially constant.

l DANIEL E. HARNE'I'I 

